When transporting relatively large quantities of many types of products, it is typically more cost effective to transport the products in bulk where the products are placed into the vehicle that is utilized to transport the product.
Depending on various factors such as the quantity of products being shipped and the distance over which the products are being shipped, the products may be transported in a rail car, a truck or a trailer. To facilitate placing the product into and/or out of the transport vehicle, the transport vehicle may include an open top.
When transporting various types of products in open top vehicles, it is possible for air movement over the product to cause a portion of the product to be blown out of the transport vehicle. Even when a relatively small portion of material is blown out of the transport vehicle, this lost material may pose problems.
For example, when coal is being hauled in open top rail cars, relatively small coal particles or dust may be blown out of the rail cars from the flow of air over the coal as the rail cars move as well as from ambient winds. Even though the amount of coal that is blown out of a particular rail car may be relatively small, the rail cars are typically moved in relatively long trains that may each have over 100 rail cars. In addition, in certain areas, many trains may travel through the same area numerous times each day, which could result in significant accumulation of the material blown out of the rail car over extended periods of time.
When the coal particles accumulate proximate to the railroad tracks over which the trains pass, the quality of the rail bed may be degraded. For example, the ability of the rail bed to properly drain water from rain or melting snow is diminished which can lead to the saturation of the rail bed and subsoil beneath the tracks. This could lead to potentially dangerous situations such as derailment of rail cars.
There have been various attempts to reduce coal particles escaping from the rail cars and contaminating the roadbed and the surrounding environment. Unfortunately, there are numerous barriers that exclude the use of a tarp or previously known mechanical closures. One example is that sometimes coal is loaded and unloaded from rail cars while they are moving. Another example is that some rail cars are completely inverted during the unloading process and prior cover designs interfere with the clamps or dumping process.
One dust controlling technique involves spraying water on top of the coal. While water initially works well, water tends to evaporate relatively fast because of the air flow over the coal pile as the rail car moves. Additionally, water tends to be in relatively short supply in some areas where coal is mined.
Another technique involves spraying water soluble chemicals over the coal to create a wind resistant crust. While these materials can last much longer than water, they are considerably more expensive than water and must be mixed with water, which can be in relatively short supply in some regions where coal is mined as noted above.
During transit, coal tends to shift which can decrease the effectiveness of the wind resistant crust. There are also potential issues relating to the water soluble materials being compatible with the power plants in which the coal is burned.
It has also been proposed to place a rigid cover over the rail car. Prior to the coal loading or unloading process, the rail car rigid cover is lifted off of the rail car. Once the process is completed, the rail car rigid cover is replaced onto the rail car.
Because of the relatively large size of the rail car rigid cover, there are challenges associated with handling the rail car rigid cover during the coal loading process at the mine and the unloading process at the power plants. Because of the fact that the rail car rigid cover handling equipment may be relatively large and the process cumbersome or in the case of bottom dump unloading it may be possible that the rail car rigid cover can remain in the closed position on the rail car during the dumping process if it has adequate venting capabilities.